In current wireless communications systems, 5 MHz˜10 MHz radio bandwidths are typically used for up to 100 Mbps peak transmission rate. Much higher peak transmission rate is required for next generation wireless systems. For example, 1 Gbps peak transmission rate is required by ITU-R for IMT-Advanced systems such as the 4th generation (“4G”) mobile communications systems. The current transmission technologies, however, are very difficult to perform 100 bps/Hz transmission spectrum efficiency. In the foreseeable next few years, only up to 15 bps/Hz transmission spectrum efficiency can be anticipated. Therefore, much wider radio bandwidths (i.e., at least 40 MHz) will be necessary for next generation wireless communications systems to achieve 1 Gbps peak transmission rate.
Orthogonal Frequency Division Multiplexing (OFDM) is an efficient multiplexing scheme to perform high transmission rate over frequency selective channel without the disturbance from inter-carrier interference. There are two typical architectures to utilize much wider radio bandwidth for OFDM system. In a traditional OFDM system, a single radio frequency (RF) carrier is used to carry one wideband radio signal, and in a multi-carrier OFDM system, multiple RF carriers are used to carry multiple radio signals with narrower bandwidth. A multi-carrier OFDM system has various advantages as compared to a traditional OFDM system such as easier backward compatibility, better reuse on legacy single-carrier hardware design, more mobile station hardware flexibility, and lower Peak to Average Power Ratio (PAPR) for uplink transmission. Thus, multi-carrier OFDM systems have become the baseline system architecture in IEEE 802.16m (i.e. for WiMAX 2.0 system) and 3GPP Release 10 (i.e. for LTE-Advanced system) draft standards to fulfill system requirements.
A multi-carrier OFDM system, however, typically has much more complicated carrier configuration. Carrier configuration generally may include the number of RF carriers, center frequency of each carrier, bandwidth of each carrier, physical index of each carrier, and sub-carrier alignment parameters of adjacent carriers, etc. Because of the complicated carrier configuration, it is difficult for mobile stations to know which RF carriers are supported by which base stations across the entire OFDM network. In current IEEE 802.16e specification, an MOB_NBR-ADV message (neighbor advertisement message) is defined for a base station to broadcast essential bandwidth and frequency information of neighboring cells on a carrier-by-carrier basis. However, such repeated broadcasting for each carrier introduces unnecessary overhead over the air and is inefficient. It thus remains a challenge to communicate global carrier configuration of the multi-carrier OFDM system effectively from base stations to mobile stations.